In Study 1, we saw that even children as old as 7-9y—whose conceptual structure seemed to be quite similar to that of adults’—nonetheless differed from adults in their application of this concept, attributing far more of the social-emotional abilities related to the HEART to both beetles and robots. How do children’s mental capacity attributions compare to adults for the larger set of target characters included in Study 2—and what does this aspect of conceptual developmental look like earlier in development (4-6y)?
Differences across age groups
Following Study 1, we projected all of children’s responses into the factor space defined by adults (standardized in terms of adults’ responses), and examined factor scores by age group (again, using the method articulated by ten Berge et al., 1999). As in Study 1, this yielded three scores for each participant, corresponding, in principle, to holistic judgments of the social-emotional, physiological, and perceptual-cognitive abilities of the target character the participant evaluated. (Note that each of these three scores takes into account adult factor loadings for all 20 mental capacities, as shown in Figure 5, Panel D.)
This allowed us to examine the effects of age group (younger children, older children, adults), factor (BODY, HEART, MIND), and target character on these scores via mixed effects Bayesian regression. As in Study 1, factor was effect-coded, and age group was dummy-coded with adults as the baseline, to assess whether children in each age group were “adult-like” in their assessments. To examine differences in mental capacity attributions to different target characters, we coded each character as either “animate” (elephant, goat, mouse, bird, beetle) or “inanimate” (computer, robot, doll, teddy bear), and included animacy status (effect-coded) as a fixed effect in our regression model. We included intercepts and slopes for individual characters as random effets in our model, along with intercepts for individual participants.
The results of this model can be found in Table 3.
Table 3: Fixed effects from a mixed-effects Bayesian regression model predicting factor scores in Study 2 by animacy status (animates, inanimates), factor (BODY, HEART, MIND), and age group (4-6y, 7-9y, adults). The model used the formula 'factor score ~ factor * age group * animacy + (1 | subject) + (1 + factor + age group | character)' and was implemented in the 'brms' package for R (Bürkner, 2017). Animacy status and factor were effect-coded; age-group was dummy-coded with adults as the baseline. Asterisks mark parameters whose 95% credible interval does not include 0.
| Parameter |
b |
Error |
95% CI |
|
| Adults |
| (Intercept) |
-0.08 |
0.07 |
[-0.23, 0.05] |
|
| HEART (vs. grand mean) |
0.03 |
0.10 |
[-0.17, 0.21] |
|
| MIND (vs. grand mean) |
0.00 |
0.17 |
[-0.35, 0.34] |
|
| characters: animates vs. inanimates |
0.49 |
0.07 |
[ 0.36, 0.63] |
* |
| characters (animates/inanimates) × HEART |
-0.26 |
0.10 |
[-0.46, -0.07] |
* |
| characters (animates/inanimates) × MIND |
-0.09 |
0.18 |
[-0.44, 0.26] |
|
| 7-9y vs. adults |
| age group (7-9y vs. adults) |
0.16 |
0.09 |
[-0.02, 0.34] |
|
| HEART × age group (7-9y/adults) |
0.51 |
0.09 |
[ 0.34, 0.69] |
* |
| MIND × age group (7-9y/adults) |
-0.44 |
0.09 |
[-0.61, -0.26] |
* |
| characters (animates/inanimates) × age group (7-9y/adults) |
-0.19 |
0.09 |
[-0.37, -0.01] |
* |
| characters (animates/inanimates) × HEART × age group (7-9y/adults) |
0.08 |
0.09 |
[-0.09, 0.26] |
|
| characters (animates/inanimates) × MIND × age group (7-9y/adults) |
-0.28 |
0.09 |
[-0.46, -0.11] |
* |
| 4-6y vs. adults |
| age group (4-6y vs. adults) |
0.08 |
0.08 |
[-0.08, 0.22] |
|
| HEART × age group (4-6y/adults) |
0.78 |
0.09 |
[ 0.61, 0.96] |
* |
| MIND × age group (4-6y/adults) |
-0.81 |
0.09 |
[-0.99, -0.62] |
* |
| characters (animates/inanimates) × age group (4-6y/adults) |
-0.26 |
0.07 |
[-0.41, -0.12] |
* |
| characters (animates/inanimates) × HEART × age group (4-6y/adults) |
0.29 |
0.09 |
[ 0.12, 0.47] |
* |
| characters (animates/inanimates) × MIND × age group (4-6y/adults) |
-0.18 |
0.09 |
[-0.36, 0.00] |
* |
By definition, adults’ factor scores did not differ across factors (HEART vs. grand mean: b = 0.03, 95% credible interval: [-0.17, 0.21]; MIND vs. grand mean: b = 0.00, 95% credible interval: [-0.35, 0.34]). As we would expect, adults attributed more mental capacities (collapsing across factors) to animates than inanimates (b = 0.49, 95% credible interval: [0.36, 0.63])—a difference that was diminished in the HEART domain (b = -0.26, 95% credible interval: [-0.46, -0.07]), but not substantially diminished in the MIND domain (b = -0.09, 95% credible interval: [-0.44, 0.26]).
As a group, 7- to 9-year-old children’s mental capacity attributions did not differ from adults, collapsing collapsing across factors and characters (b = 0.16, 95% credible interval: [-0.02, 0.34])—but this masks several important differences between older children and adults. As in Study 1, older children’s scores were characterized by a relative over-attribution of abilities in the HEART domain (b = 0.51, 95% credible interval: [0.34, 0.69]), and a relative under-attribution of abilities in the MIND domain (b = -0.44, 95% credible interval: [-0.61, -0.26]). Collapsing across factors, older children made less of a distinction between animate an inanimate target characters, relative to adults (b = -0.19, 95% credible interval: [-0.37, -0.01]). This relative under-differentiation of animate and inanimate characters was particularly pronounced in the MIND domain (b = -0.28, 95% credible interval: [-0.46, -0.11]).
How did younger children compare to adults? As a group, 4- to 6-year-old children’s mental capacity attributions did not differ from adults, collapsing collapsing across factors and characters (b = 0.08, 95% credible interval: [-0.08, 0.22])—but again, this masks a variety of developmental differences that generally parallel the differences between older children and adults just described. Much like older children, younger children’s scores were characterized by a relative over-attribution of abilities in the HEART domain (b = 0.78, 95% credible interval: [0.61, 0.96]) and a relative under-attribution of abilities in the MIND domain (b = -0.81, 95% credible interval: [-0.99, -0.62]), and they differentiated less between animate an inanimate target characters than did adults (b = -0.26, 95% credible interval: [-0.41, -0.12]). This relative under-differentiation of animate and inanimate characters was particularly pronounced in the MIND domain (b = -0.18, 95% credible interval: [-0.36, 0.00]), and less pronounced in the HEART domain (b = 0.29, 95% credible interval: [0.12, 0.47]).

A visual inspection of Figure 6 further clarifies these findings.
In the BODY domain, a distinction between animate and inanimate target characters was clearly present in all age groups, though slightly attenuated among 4- to 6-year-old children (see Figure 6, Panel A, top row). A closer look at factor scores for individual characters (Panel B, top row) suggests that younger children diverged from adults primarily in their attributions to the “edge cases” that were the focus of Study 1: the robot (to which they over-attributed the physiological sensations related to the BODY), and the beetle (to which they under-attributed such BODY capacities). Older children’s BODY attributions were generally indistinguishable from adults’ for almost all target characters. (The only possible exception is the bird—but, in our view, it appears that this was driven by adults slightly under-attributing BODY capacities to this character.)
In the HEART domain, the distinction between animate and inanimate target characters was subtler across all age groups, and the degree of distinction did not vary dramatically with age (see Figure 6, Panel A, middle row). Instead, children generally over-attributed HEART to both animates and inanimates; these over-attributions declined between 4-6y and 7-9y of age, but did not reach adult-like levels even among older children. This is consistent with Study 1, in which 7- to 9-year-old children over-attributed HEART to both the beetle and the robot, relative to adults. In this study, older children again attributed more HEART capacities to the beetle and the robot, but also to the mouse and the goat (see Panel B, middle row). Relative to other animates, adults attributed particularly few HEART capacities to the mouse and the goat—perhaps because of their respecive statuses as vermin and food animals in this cultural context.
Finally, in the MIND domain, neither group of children made a robust distinction between animates and inamates—but adults clearly did (see Figure 6, Panel A, bottom row). Instead, children generally under-attributed MIND to both animates and inanimates. These under-attributions became less dramatic between 4-6y and 7-9y of age, and by 7-9y children’s MIND attributions to inanimates were adult-like. But even at 7-9y, children did not attributed as many MIND capacities to animates as did adults; between 7-9y and adulthood, MIND attributions increased for all of the animate characters, and particularly dramatically for the bird, the mouse, and the elephant (see Figure 6, Panel B, bottom row).
The raw data further supporst these observations; see Figure 7 for raw counts of no, kinda, and yes responses for all items, grouped by factor, animacy status (Panels A-C) or character (Panels D-F), and age group. For example, consider pain (the first capacity under BODY): Across age groups, most participants said that an elephant could feel pain, with the proportion of “yes” responses increasing across age groups; meanwhile, few participants said that a computer could feel pain, with the proportion of “yes” responses decreasing across age groups. More dramatic changes are evident in the HEART and MIND factors, with attributions of HEART generally decreasing across age groups (especially to inanimate target characters - e.g., the computer, the robot), and attributions of MIND generally increasing across age groups (especially to animate target characters - e.g., the mouse, the goat, the elephant). (See SOM for an analysis, parallel to the regression analyses here, of the proportion of the top-loading mental capacities for each factor that were endorsed by participants of different ages.)

Age differences within the child samples
As in Study 1, we were interested not only in differences across age groups, but also across the—even wider—age range within our child samples. In Study 2, this included children as young as 4 years up to nearly 10 years of age. This allowed us to look at age-related differences in mental capacity attributions across a wide period from early to middle childhood.
To explore age-related differences continuously within the child samples, we conducted an additional regression analysis on children’s factor scores alone, including interactions with exact age in years (centered at the mean: 6.73y) rather than age group. (See Table 4 for the full results of this model, and Figure 8 for a visualization of changes in children’s factor scores across the age range.)
This analysis confirmed that, relative to the grand mean, attributions of HEART decreased with age (b = -0.09, 95% credible interval: [-0.14, -0.04]) and attributions of MIND increased with age (b = 0.13, 95% credible interval: [0.07, 0.18]). These findings are both in line with the age group analysis described in the previous section, suggesting that the observed group differences correspond to gradual developmental differences as children’s responses become increasingly adult-like.
If children were also becoming increasingly adult-like in their distinctions between animate and inanimate target characters, we would also expect the overall animate-inanimate distinction (collapsing across factors) to increase with age, driven primarily by increases in the BODY and especially MIND domains. Instead, collapsing across factors, the general distinction between animates and inanimates did not differ with age (b = 0.01, 95% credible interval: [-0.02, 0.05]); decreased in the HEART domain, relative to the grand mean (b = -0.06, 95% credible interval: [-0.11, -0.01]); and did not change substantially in the MIND domain (but, if anything, decreased: b = -0.04, 95% credible interval: [-0.09, 0.01]), as we might expect if older children were approaching “adult-like” responses in this aspect of their mental capacity attributions.
We speculate on several possible explanations of these unexpected findings in the Study 2 discussion section, below. For now, we note that participants who assessed the robot seemed to become particularly un-adult-like at older ages, and excluding these participants yields a more coherent picture of increasing adult-like-ness with increasing age (see Figure 8, Panel A, turquoise lines and points). This did not appear to be the case when excluding any of the other inanimate target characters (computer, teddy bear, doll).
Table 4: Fixed effects from a mixed-effects Bayesian regression model of children's responses, predicting factor scores in Study 2 by animacy status (animates, inanimates), factor (BODY, HEART, MIND), and exact age. The model used the formula 'factor score ~ factor * age * animacy + (1 | subject)' and was implemented in the 'brms' package for R (Bürkner, 2017). Factor and animacy were effect-coded, and age was mean-centered. Asterisks mark parameters whose 95% credible interval does not include 0.
| Parameter |
b |
Error |
95% CI |
|
| Collapsing across age |
| (Intercept) |
0.04 |
0.05 |
[-0.07, 0.15] |
|
| HEART (vs. grand mean) |
0.68 |
0.09 |
[ 0.49, 0.86] |
* |
| MIND (vs. grand mean) |
-0.64 |
0.15 |
[-0.94, -0.35] |
* |
| characters: animates vs. inanimates |
0.27 |
0.05 |
[ 0.16, 0.38] |
* |
| characters (animates/inanimates) × HEART |
-0.07 |
0.09 |
[-0.25, 0.11] |
|
| characters (animates/inanimates) × MIND |
-0.31 |
0.14 |
[-0.58, -0.02] |
* |
| Age effects |
| age (centered at the mean) |
0.03 |
0.02 |
[ 0.00, 0.07] |
|
| HEART × age |
-0.09 |
0.03 |
[-0.14, -0.04] |
* |
| MIND × age |
0.13 |
0.03 |
[ 0.07, 0.18] |
* |
| characters (animates/inanimates) × age |
0.01 |
0.02 |
[-0.02, 0.05] |
|
| characters (animates/inanimates) × HEART × age |
-0.06 |
0.03 |
[-0.11, -0.01] |
* |
| characters (animates/inanimates) × MIND × age |
-0.04 |
0.03 |
[-0.09, 0.01] |
|
